Download Chapter 21 Powerpoint lecture

TORTORA • FUNKE
Skin
• CASE
Microbiology
Describe the structure of the skin and mucous membranes and the
ways pathogens can invade the skin.
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
Chapter 21
• Skin is a physical
and chemical barrier
against microbes
• Moist areas support
more microbes
Microbial Diseases of the Skin and Eyes
• Salt inhibits microbes
• Lysozyme
hydrolyzes
peptidoglycan
• Fatty acids inhibit
some pathogens
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Skin
Figure 21.1
Mucous Membranes
Describe the structure of the skin and mucous membranes and the
ways pathogens can invade the skin.
• Epidermis contains keratin,
waterproof coating
• Line body cavities
• Dermis contains hair follicles, sweat
ducts, oil glands that provide
passageways for microbes
• Epithelial cells attached to an extracellular matrix
• Cells secrete mucus
• Sebum and sweat are secretions of
skin that help inhibit microbes
• Some have cilia
• Body cavities lined with epithelial
cells, some secrete mucus as part of
mucus membrane
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.1
Normal Microbiota of the Skin
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Microbial Diseases of the Skin
Provide examples of normal skin microbiota, and state their locations and
ecological roles.
• Vesicles = small fluid-filled lesions
• Skin microbes resistant
to desiccation and salt
• Bullae = vesicles > 1 cm
• Gram-positive, salttolerant bacteria
dominate on skin
• Papules are raised lesions
• Macules are flat reddened lesions
• Pustules are raised lesions with pus
• Staphylococci
• Exanthem
• Micrococci
• Skin rash arising from another focus of infection
• Diphtheroids
• Enanthem
• Never completely
removed by washing
• Mucous membrane rash arising from another
focus of infection
• Some grow on skin oil
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.1a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
1
Microbial Diseases of the Skin (Lesions)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.2
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Staphylococcal Skin Infections
Differentiate staphylococci from streptococci, and list several skin infections
caused by each.
• S. epidermidis (majority of skin microbiota)
• Gram-positive cocci, coagulase-negative
• Staphylococcus aureus
• Gram-positive cocci, coagulase-positive
• Leukocidin
• Exfoliative toxin
• Can produce penicillinase, therefore treated with
vancomycin
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Staphylococcal Skin Infections
•
Slimeproducing
bacteria
adhere to
surfaces
like
catheter,
then divide
until surface
coated with
biofilm
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.3
2
Staphylococcal Skin Infections – S. aureus
Staphylococcal Skin Infections – S. aureus
• Localized infections from S. aureus entering skin
openings:
• Folliculitis
• Impetigo of the newborn
• Infections of hair follicles
• Toxemia when toxins
enter bloodstream
• Sty
• Folliculitis of an eyelash
• Scalded skin syndrome
• Furuncle
• Toxic shock syndrome
• Abscess; pus surrounded by inflamed tissue
• Carbuncle
• Inflammation of tissue under the skin
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Streptococcal Skin Infections
Figure 21.4
Streptococcal Skin Infections
• Streptococcus
pyogenes
• Erysipelas – reddish
patches
• Gram + cocci often in
chains
• Classified by:
• Group A betahemolytic
streptococci –
pathogens most
important to
humans
• M proteins on fuzzy
layer of surface
fibrils
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Impetigo – isolated
pustules (usually
streptococci)
Figure 21.5
Invasive Group A Streptococcal Infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Infections by Pseudomonads
List the causative agent, method of transmission, and clinical symptoms of
Pseudomonas, dermatitis, otitis externa, acne.
• Invasive group A
beta-hemolytic
streptococci cause
severe and rapid
tissue destruction
• Pseudomonas aeruginosa
• Gram-negative, aerobic rods, primarily in soil and water
• Produces endotoxin and several exotoxins
• Streptokinases
• Resistant to many disinfectants and antibiotics
• Hyaluronidase
• Pyocyanin pigment produces a blue-green pus
• Exotoxin A,
superantigen
• Pseudomonas dermatitis
• Cellulitis
• Post-burn infections
• Necrotizing fasciitis
• Respiratory infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.6, 7
• Otitis externa
Figure 21.8
• Treated by fluoroquinolones
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
3
Calculate the relative risk to determine the most
likely source of Pseudmonas dermatitis
Exposure
Exposed
(a) Have
(b) No Rash
Rash
What was the mostly likely source of this outbreak
of Pseudmonas dermatitis?
Not Exposed
(c) Have
(d) No Rash
Rash
Exposure
Relative Risk
Restaurant
18
11
1
Arcade
10
6
9
6
Restaurant
1.24
Swimming
pool
Exercise
room
17
1
2
11
Arcade
1.04
11
5
8
7
Swimming pool
6.14
18
2
1
10
Exercise room
1.29
Hot tub
9.90
Hot tub
e=
a
a+b
c
c+d
f=
1
Relative Risk =
e
f
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Acne
Warts
• Comedonal acne
• Occurs when sebum channels are blocked with shed
skin cells
• Inflammatory acne from metabolic end-products
• Propionibacterium acnes – metabolizes sebum
• Gram-positive, anaerobic rod
• Treatment:
• Preventing sebum formation (isotretinoin)
• Antibiotics
• Benzoyl peroxide to loosen clogged follicles
• Visible (blue) light (kills P. acnes)
• Nodular cystic acne
• Treatment: isotretinoin
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
List the causative agent, method of transmission, and clinical
symptoms of these skin infections: warts, smallpox, chickenpox,
shingles, cold sores, measles, rubella, fifth disease, roseola.
• Papillomaviruses – cause skin cells to proliferate and
produce benign growth called wart or papilloma
• Treatment:
• Removal
• Imiquimod (stimulate interferon production)
• Interferon
• Spread by direct contact
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Poxviruses
Herpesviruses (chickenpox)
• Smallpox (Variola)
• Smallpox virus (Orthopox
virus)
• Varicella-zoster virus
(Human herpes virus 3)
• Transmitted by respiratory
route, moved to skin via
bloodstream
• Complications include
encephalitis and Reye’s
syndrome
• Variola major has 20%
mortality
• Transmitted by the
respiratory route
• Variola minor has <1%
mortality
• Causes pus-filled
vesicles
• Eradicated worldwide via
vaccination
• Virus may remain latent
in dorsal root ganglia
• Monkeypox
• Prevention by smallpox
vaccination
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.9
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.10a
4
Shingles
Herpes simplex 1 and Herpes simplex 2
• Human herpes virus 1 (oral, respiratory) and HHV-2 –
often latent in nerve cells
• Reactivation of latent
HHV-3 releases
viruses that manifest
as vesicular rash along
peripheral nerves to
skin.
• Cold sores or fever blisters (vesicles on lips)
• Herpes gladiatorum (vesicles on skin)
• Herpes whitlow (vesicles on fingers)
• Herpes encephalitis (HHV-2 has up to a 70% fatality
rate)
• Treated with acyclovir
and an attenuated live
vaccine available
• HHV-1 can remain latent in trigeminal nerve ganglia
• HHV-2 can remain latent in sacral nerve ganglia
• Acyclovir may lessen symptoms
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.10b
Cold sores or fever blisters caused by herpes
simplex virus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Site of latency of human herpesvirus type 1
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Measles (Rubeola)
Measles (Rubeola)
• Measles virus
• Transmitted by respiratory
route
• Macular rash and Koplik's
spots
• Prevented by vaccination
for longterm immunity
• Encephalitis in 1 in 1000
cases
• Subacute sclerosing
panencephalitis in 1 in
1,000,000 cases
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.14
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.13
5
Rubella (German Measles)
• Rubella virus
• A 1905 list of skin rashes included #1-measles, #2scarlet fever, #3-rubella, #4-Filatow-Dukes (mild scarlet
fever), and #5-
• Transmitted by
respiratory route
• Macular rash and
fever
• Fifth Disease
• Human parvovirus B19 produces mild flu-like
symptoms and facial rash
• Congenital rubella
syndrome causes
severe fetal
damage
• Roseola
• Human herpesvirus 6 causes a high fever and rash,
lasting for 1-2 days
• Prevented by
vaccination
(unknown duration)
Figure 21.15
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cutaneous Mycoses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cutaneous Mycoses (Dermatomycoses)
Differentiate cutaneous from subcutaneous mycoses, and provide an example
of each.
• Dermatomycoses: tineas or ringworm, fungi that
colonize outer layer of epidermis
• Metabolize keratin (hair, skin, nails)
• Trichophyton
infects hair, skin, nails
• Epidermophyton
infects skin and nails
• Microsporum
infects hair and skin
• Treatment (antifungal)
• Oral griseofulvin
• Topical miconazole
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Subcutaneous Mycoses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.16
Candidiasis
List the causative agent of and predisposing factors for candidiasis.
• Sporotrichosis
• Candida albicans (yeast) – opportunistic and may
proliferate when normal bacteria suppressed
• Sporothrix schenckii enters puncture wound from
soil
• Candidiasis may result from suppression of competing
bacteria by antibiotics
• Grow and produce subcutaneous nodules along
lymphatic vessels
• Occurs in skin; mucous membranes of genitourinary
tract and mouth
• Treated with KI (potassium iodide)
• Thrush is an infection of mucous membranes of mouth
• Topical treatment with miconazole or nystatin
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
6
Candidiasis
Scabies
• Sarcoptes scabiei burrows in the skin to lay eggs
• Treatment with topical insecticides
List the causative agent,
method of transmission,
clinical symptoms, and
treatment for scabies
and pediculosis.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.17
Pediculosis
Figure 21.18
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Microbial Diseases of the Eye
• Conjunctiva = mucous membrane lining eyelid and
covering eyeball
• Pediculus humanus
capitis (head louse)
• Conjunctivitis (pinkeye)
• P. h. corporis (body
louse)
• Various microbes
Define conjunctivitis.
• Haemophilus influenzae
• Associated with unsanitary contact lenses
• Feed on blood
• Neonatal gonorrheal ophthalmia
• Lay eggs (nits) on
hair
• Neisseria gonorrhoeae
• Transmitted to newborn's eyes during passage
through the birth canal
• Treatment with
topical insecticides
• Prevented by treatment newborn's eyes with
antibiotics
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.19
Microbial Diseases of the Eye
• Chlamydia trachomatis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Microbial Diseases of the Eye – Trachoma lesions
List the causative agent, method of transmission, and clinical symptoms of
these eye infections: neonatal gonorrheal ophthalmia, inclusion
conjunctivitis, trachoma.
• Inclusion conjunctivitis
• Transmitted to newborn's eyes during passage
through the birth canal
• Spread through swimming pool water
• Treated with tetracycline
• Trachoma
• Greatest cause of blindness worldwide
• Infection causes permanent scarring; scars
abrade the cornea leading to blindness
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.20
7
Microbial Diseases of the Eye
Trophozoite of Acanthamoeba, cause of A. keratitis
List the causative agent, method of transmission, and clinical symptoms of
these eye infections: herpetic keratitis, Acanthamoeba keratitis.
• Herpetic Keratitis
• Herpes simplex virus 1 (HHV-1) invades central
nervous system
• Inflammation of cornea, may cause blindness
(corneal ulcers)
• Treated with trifluridine
• Acanthamoeba keratitis
• Transmitted from water
• Associated with unsanitary contact lenses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21.21
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
8